The present invention relates generally to radio frequency (RF) signal filters, and more particularly to a surface-mount filter that couples the printed circuit boards of radio transceivers.
Interconnection to prior art ceramic block filters may be accomplished by integral conventional coupling connectors as shown and described in U.S. Pat. No. 4,431,977 or by integral coaxial coupling cables retained by a housing as shown and described in U.S. Pat. No. 4,742,562. However, in both of the foregoing instances coaxial cables are required for interconnection, thereby incurring additional cost.
The need for coaxial cables may be eliminated by surface mounting the filter and coupling to the resonators thereof by direct solder connection as shown and described in U.S. Pat. No. 4,673,902. However, direct solder connections to the ceramic block are not reliable since small protrusions i the circuit board may result in open connections. Alternatively, wires may be connected to the resonators as shown and described in U.S. Pat. No. 4,703,291 or to input/output pads as shown and described in U.S. Pat. No. 4,716,391. However, the use of individual wires likewise both increases the manufacturing cost and is unreliable. Therefore, there is need for a surface-mount filter that reliably and inexpensively surface mounts to printed circuit boards of radio transceivers.